Ed Miliband’s dramatic proposal is to end the levy some union members automatically pay to Labour and replace this with voluntary contributions.

In future, instead of having the option of opting out of this levy, union members would have to opt in. They would become members of the Labour Party in the process.

These contributions are worth around £8 million a year to Labour. A new opt-in system could cost the party about £5 million in lost revenue.

The Labour leader wants limits introduced for parliamentary selection contests. He wants to curb how much unions and other organisations can spend.

He also favours a shake-up of party funding, with a cap on donations from businesses, unions and individuals.

Miliband is proposing a system of US-style “primaries” in constituencies. This would mean everyone registered as a Labour supporter, rather than just Labour members, could vote for a candidate to stand in an election.

Miliband didn’t mind being elected over his brother on the back of union votes. This is one reason some union leaders are furious.